Investment Securities (Contractual Maturity Distribution Of Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Within one year, Amortized Cost	$ 86
After one year through five years, Amortized Cost	551
After five years through ten years, Amortized Cost	125
After ten years, Amortized Cost	9,030
Subtotal, Amortized Cost	9,792
Within one year, Fair Value	86
After one year through five years, Fair Value	557
After five years through ten years, Fair Value	124
After ten years, Fair Value	9,269
Subtotal, Fair Value	10,036
Total investment securities available-for-sale, Amortized Cost	10,060	9,901
Total investment securities available-for-sale, Fair Value	10,297	10,104
Auction-Rate Preferred Securities [Member]
Total investment securities available-for-sale, Amortized Cost	163	423
Total investment securities available-for-sale, Fair Value	156	408
Money Market And Other Mutual Funds [Member]
Total investment securities available-for-sale, Amortized Cost	105	93
Total investment securities available-for-sale, Fair Value	$ 105	$ 93